ArrayList

[newbie29]

Hi,

I have an ArrayList, ethernet, of objects, class Ethernet. I am trying to change the contents of one of the objects in the ArrayList. However, I am unable to.

Here is a sample of what I'm tying to do:

((Ethernet) ethernet.get(1)).avgNor = 99;

The value in avgNor remains to what it was originally, no changes occur.

I appreciate your help.

Thanks,
N29

[ray326]

That gets you a copy, not access to the object in the list. You'll need to get the object, change the value and put it back into the list.

[sjalle]

I suspect the sample code :

((Ethernet) ethernet.get(1)).avgNor = 99;

is not where the error is.
It indicates that avgNor is a numeric and also a public member
of the Ethernet class, if the above compiles then the error is elsewhere.

import java.util.*;

class IntClass {
  public int value=0;
  public IntClass (int value) {
    this.value=value;
  }
}
public class Stuff {
  ArrayList list=new ArrayList();
  public Stuff() {
    for (int i=0; i<10; i++) {
      list.add(new IntClass(i));
    }
    for (int i=0; i<list.size(); i++) {
      System.out.print( ((IntClass)list.get(i)).value+" ");
    }
    System.out.println("");

    ((IntClass)list.get(5)).value=200; // works like a dream

    for (int i=0; i<list.size(); i++) {
      System.out.print( ((IntClass)list.get(i)).value+" ");
    }
  }
  public static void main(String[] args) {
    Stuff stuff1 = new Stuff();
  }
}

Output:

0 1 2 3 4 5 6 7 8 9 
0 1 2 3 4 200 6 7 8 9

The get method of ArrayList does not give a copy of anything
else but the object address .

[ray326]

Thanks for the example.